The present application relates to an imaging apparatus and, more particularly, to a lens adapter in which an optical component such as a conversion lens is mounted and also to an imaging apparatus using the lens adapter.
From the past, digital still cameras have often incorporated retractable zoom lenses. In this kind of digital still camera, a zoom optical system is housed in a camera body. Thus, the zooming function is accomplished without spoiling the thinness of the camera. Normally, when the power supply for the camera body is turned on, the zoom lens projects forwardly. When the power supply is turned off, the lens is retracted into the camera body.
However, only with the zoom lens incorporated in the camera body that has been thinned, the magnification is restricted. Therefore, in order to obtain images at high magnifications, it is necessary to install a separate tele-conversion lens or other optical component onto the lens barrel. A digital still camera having such an optical component that can be mounted onto the lens barrel is described, for example, in patent reference 1 (JP-A-2000-235222). In the digital still camera described in this patent reference 1, a cylindrical lens accommodation portion in which a zoom lens unit is housed protrudes from the front surface of the camera body. A threaded groove is formed in the inner wall of the lens accommodation portion. Furthermore, a threaded groove is formed at one end of the tele-conversion lens. The optical component is mounted without applying a load to the zoom optical system by screwing the tele-conversion lens into the threaded groove in the lens accommodation portion. When the tele-conversion lens is not in use, it is removed from the lens accommodation portion.
However, in the digital still camera in which an optical component such as a tele-conversion lens is screwed into the lens accommodation portion formed in the camera body, it is necessary to secure a region where plural turns of threaded grooves are formed. Therefore, it may be required that the lens accommodation portion protrude ahead of the camera body. The lens accommodation portion protrudes from the camera body at all times, i.e., even when no tele-conversion lens is mounted. In the camera body that has been thinned, forward protrusion of the lens accommodation portion impairs portability and design.
On the other hand, if the number of threaded grooves formed in the lens accommodation portion is made fewer, and if the amount of protrusion of the lens accommodation portion is reduced, the thinness of the camera body is not deteriorated but there is the possibility that the reliability with which a connection is made with the tele-conversion lens is deteriorated.